gistdiff

Generate commit messages from a git diff using the Vercel AI Gateway.

Pipe any diff to gistdiff and get back a conventional-commit-style subject line — or the full subject + body, ready to pass straight to git commit -F -. One API, swap models freely.

Install

npm i -g gistdiff

Requires Node.js 20+.

Setup

gistdiff talks to the Vercel AI Gateway, so you need an API key.

export AI_GATEWAY_API_KEY=your_key_here

You can also drop it in a .env.local at the repo root where you run the command — gistdiff will pick it up automatically.

Usage

# Subject line only (the default)
git diff --cached | gistdiff

# Subject + body, piped straight into a commit
git diff --cached | gistdiff -d | git commit -F -

# Compare the default Anthropic + OSS models side-by-side
git diff --cached | gistdiff -c

# Compare specific models
git diff --cached | gistdiff -c openai/gpt-5,xai/grok-4

# Branch / PR summary
git diff main...feature | gistdiff -d

Flags

| Flag | Description | |---|---| | -m, --model <id> | Gateway model id (default: anthropic/claude-sonnet-4.6) | | -d, --description | Include a body paragraph, not just the subject | | -c, --compare [ids] | Run multiple models side-by-side. Bare flag uses the built-in defaults; pass a comma-separated list to override. | | --list-models | List available gateway models and exit | | --json | Machine-readable JSON output |

License

ISC © Joe McKenney